Jack Fouquette (1975) observed reproductive character displacement between the chorus frogs, Pseudacris feriarum and Pseudacris nigrita, with P. feriarum increasing its pulse rate and number in areas of sympatry. Extensions of Fouquette's original study by Lemmon (2009 and 2010) observed this similar displacement along the contact zone in the southeastern United States and found that the displacement was occurring due to female preference pressures on male P. feriarum in order to avoid maladaptive hybridization. In this study, which is an extension of Fouquette (1975) and Lemmon (2009), I compare the acoustic recordings from Fouquette's original study to present-day populations of P. feriarum and P. nigrita across the contact zone. Randomization test results show that different populations from around the contact zone have changed over time in regards to dominant frequency and call duration, but have not changed in regards to pulse rate or number, possibly indicating that female preference selection pressures are still strong on P. feriarum males in sympatry for higher energy calls.

Milthorpe, H. (2014). A Comparison of Past and Present Pseudacris feriarum and Pseudacris nigrita
Populations: Reproductive Character Displacement in Areas of Sympatry Over Time. Retrieved from http://purl.flvc.org/fsu/fd/FSU_migr_uhm-0328